The present invention relates to an apparatus and method of cryoablation, and more particularly for cryoablation using multiple probes introduced into the body of a patient through a common introducer, so as to perform cryoablation of a particular volume of tissue while minimizing damage to adjacent healthy tissues.
A variety of medical conditions are preferentially treated by ablation of tissues within the body. Classically, ablation was performed using invasive surgical procedures requiring cutting or destroying tissues between the exterior of the body and the particular site whose ablation is desired. More recently, less invasive procedures have been developed, which bring about the destruction of selected tissues using a probe or probes which penetrate to the area to be operated, and destroy the selected tissue by transferring energy to those tissues; RF energy, light (laser) energy, microwave energy, and high-frequency ultra-sound energy are among the forms which have been used. However all such methods have the common disadvantage that while transferring energy to the tissues whose destruction is intended, they tend also to transfer energy, through conduction, convection, and other natural processes, to nearby healthy tissues as well. All such energy transfer methods ultimately result in heat release, causing complications and adverse effects. Noticeable pain results, the functioning of nearby healthy tissues is impaired, and the healthy tissues are often damaged or destroyed. Moreover, in some cases tissues exposed to thermal energy or other forms of energy that raise their temperatures secrete substances that may be toxic to adjacent healthy tissues.
In contrast, cryoablation provides a number of important advantages over other ablation techniques. Cryoablation provides better control of the ablated volume than is attainable using other procedures. Moreover, real-time imaging during cryoablation, using ultrasound and MRI techniques, is helpful and straightforward, since the frozen tissue is clearly seen under these imaging techniques. Also, cryoablation, unlike heat radiation techniques, allows for repeatable and/or complementary treatment of the affected area. Cryoablation is considered to cause less pain to the patients. Some scientific evidence supports the conclusion that there is less morbidity and less risk of mortality as a result of cryoablation procedure compared to other minimally invasive and traditional techniques. For these and other reasons, cryoablation has recently become a popular method for certain types of minimally invasive ablation procedures. Examples include the treatment of prostate malignant tumors and of benign prostate hyperplasia (BPH), and the creation of trans-myocardial channels to effect trans-myocardial revascularization.
Yet, cryoablation procedures also have an inherent disadvantage. Cryoprobes when activated typically form at their tip what is know in the art as an xe2x80x9cice ballxe2x80x9d, a volume which is frozen by exposure to the low temperatures developed by the cryoprobe. Unfortunately, the radius of the volume in which total destruction of tissues is achieved (such destruction of tissues being the purpose of the operation) is typically only half of the radius of the volume within which tissues are more or less severely damaged. Since the volume of a sphere is proportional to the cube of the radius, the volume of total cell destruction, for a particular ice-ball, will typically be only the order of one-eighth of the volume of the area that is frozen during the operation and more or less severely damaged. The disadvantage is clear: if a single ice-ball is used to destroy a selected volume, and the ice-ball is large enough to ensure the complete destruction of that volume (which complete destruction would be desired in the case of a malignancy, for example), then a surrounding volume approximately seven times larger will be more or less severely damaged. That surrounding volume will typically include much healthy tissue that would preferably be left healthy and intact. In the case of ablation of the prostate, for example, freezing of surrounding tissues using simple cryosurgical techniques will typically damage or destroy, and create temporary or permanent impairment of the function of, the prostatic urethra, the anus, and various bundles of nerves in the prostatic area.
One method of solving this problem is taught by U.S. Pat. No. 6,142,991 to Schatzberger, teaching the use of a series of ice-balls of small dimensions, such as can be created by a two-dimensional array of cryoprobes whose depth of penetration can be measured and controlled, so as to achieve accurate three-dimensional placement of a plurality of ice-balls, in a manner that conforms to the dimensions and form and placement of the lesion to be destroyed. In other words, Schatzberger""s apparatus defines a volume of controllable form and dimension, for cryoablation. The ice-balls created by the apparatus are each of small dimensions, and they are placed so as to be contiguous to one another or to overlap each other. This arrangement results in a reduction of the amount of tissue that is damaged but not destroyed, and permits more accurate definition of the exact form and dimensions of the ablated tissue.
The mechanism described by Schatzberger is not, however, well adapted to every application of cryoablation. It is relatively complex, and requires penetration of the affected area by a multiplicity of individually introduced and individually handled cryoprobes. It could not be used, for example, in the context of cryoablating benign prostate hyperplasia (BPH) through the urethra, a relatively non-invasive treatment method described in U.S. patent application Ser. No. 09/301,576, filed Apr. 29, 1999, and incorporated herein by reference. That procedure requires an apparatus which is both more simple and more compact than that described by Schatzberger, in that the procedure requires the operating portion of the cryogenic apparatus to be introduced to the area of the lesion by means of a cystoscope, in order to reduce reducing trauma to healthy tissue.
Thus there is a widely recognized need for, and it would be highly advantageous to have, a method and apparatus for cryoablation that provides for the destruction of a defined volume of tissue, yet which minimizes damage to adjacent tissues. It would be further advantageous to have a method of cryoablation using an apparatus that creates such an extended volume of cryoablation yet is contained within a single introducer. It would be yet further advantageous to have such an introducer which could be introduced through an operating channel of a catheter or cystoscope, enabling it to reach the proximity of the region to be treated with a minimum of trauma to intervening tissues.
Referring now to another aspect of prior art, two-stage heating and cooling has successfully been used in surgical cryoablation systems, particularly in two-stage cooling of a high-pressure gas used to achieve cryogenic temperatures using Joule-Thomson heat exchangers. Two-stage cooling presents the advantages of more rapid and more efficient cooling than would be possible in a single Joule-Thomson cooling stage. In U.S. Pat. No. 5,993,444 to Ammar a cryogenic probe utilizes two stages of Joule-Thomson cooling to achieve low temperatures at the operating end of the probe. Ammar describes, however, a single probe so cooled.
Schatzberger, in the patent previously cited, describes two-stage cooling in a multi-probe system. In FIG. 6a Schatzberger teaches a plurality of cryosurgical probes connected by flexible connectors to a common housing which includes a pre-cooling element for pre-cooling the high-pressure gas flowing to the probes, this element being preferably a Joule-Thomson heat exchanger used as a cooler. Schatzberger""s system thus utilizes two-stage cooling, with pre-cooling taking place extracorporeally in the housing and a second cooling stage taking place in each individual cryoprobe. Furthermore, the mechanism Schatzberger describes has the disadvantage that the pre-cooled gases must be transported a considerable distance between the housing and the probe, and the conduit connecting the probe to the housing, which must remain flexible, must also be thermally insulated.
Consequently, it would be further advantageous to have a cryoablation apparatus and method which enables the pre-cooling of a plurality of cryoprobes within a single introducer, such that the pre-cooling stage of a two-stage Joule-Thomson heat exchange process can take place in close proximity to a second stage of cooling which takes place within the individual cryoprobes.
According to one aspect of the present invention there is provided a cryosurgery apparatus comprising an introducer having a hollow and a distal portion, the distal portion being sufficiently sharp so as to penetrate into a body, the hollow of the introducer being designed and constructed for containing a plurality of cryoprobes each of the cryoprobes being for effecting cryoablation, such that each of the plurality of cryoprobes is deployable through the distal portion of the introducer when the distal portion is positioned with respect to a tissue to be cryoablated.
According to further features in preferred embodiments of the invention described below, the introducer comprises a cooling device designed and constructed to cool the hollow of the introducer, and a heating device designed and constructed to heat the hollow. The cooling device and heating device may be a combined heating/cooling device, such as a Joule-Thomson heat exchanger.
According to still further features in the described preferred embodiments, the introducer includes a heating and cooling device for pre-heating and pre-cooling gasses which are passed through at least a portion of the introducer and are subsequently delivered to at least one of the cryoprobes. The heating and cooling device will preferably be a Joule-Thomson heat exchanger. The introducer will further comprise a heat-exchanging configuration for exchanging heat between a gas passed to at least one of a plurality of cryoprobes and the heating and cooling device. A thermal sensor, such as a thermocouple, will preferably be used to monitor temperature in the hollow.
According to still further features in the described preferred embodiments, the introducer is designed and constructed to be coupled to at least one high-pressure gas source, the gas source being coupleable to a Joule-Thomson heat exchanger having a Joule-Thomson orifice in the introducer. The gas source may be a source of at least one gas selected from a group consisting of high-pressure argon, high-pressure nitrogen, high-pressure air, high-pressure krypton, high-pressure CF4, high-pressure N2O, and high-pressure carbon dioxide. The gas source may also be a source of high-pressure helium. The introducer is designed and constructed so as to facilitate exchange of heat between two temperature states of gas from the high-pressure gas source, gas in a first state being at a first temperature prior to passing through the Joule-Thomson orifice, and gas in a second state being at a second temperature subsequent to passing through the Joule-Thomson orifice.
According to still further features in the described preferred embodiments, the introducer is designed and constructed to be coupled both to a first gas source and to a second gas source. The gas provided by the first gas source is cooled by expansion and may liquefy when passing through a Joule-Thomson orifice. The gas provided by the second gas source has an inversion temperature lower than the temperature obtained by liquefaction of gas provided by the first gas source. The apparatus further comprises control elements for regulating a flow of gas from the first gas source and the second gas source.
According to still further features in the described preferred embodiments, the introducer further comprises a plurality of cryoprobes contained therein. The distal end of the introducer is formed with a plurality of openings for deployment therethrough of the cryoprobes. Preferably, at least one of the plurality of cryoprobes is coolable, and the coolable cryoprobe is also heatable. Preferably, the cryoprobes comprise a Joule-Thomson heat exchanger having a Joule-Thomson orifice, for heating and cooling the cryoprobes.
According to still further features in the described preferred embodiments, the hollow of the introducer is partitioned into a plurality of longitudinal compartments, each of the plurality of longitudinal compartments is designed and constructed for containing at least one of the plurality of cryoprobes.
According to still further features in the described preferred embodiments, the introducer comprises thermal insulation designed and constructed so as to hinder the passage of heat between the hollow of the introducer and tissues of the body, when the introducer is positioned within the body.
According to still further features in the described preferred embodiments, the introducer comprises a heat-exchanging configuration. The heat-exchanging configuration may include a porous matrix, which may include a conduit tunneling through at least a portion of the porous matrix, and which may include a spiral conduit integrated with the porous matrix.
According to still further features in the described preferred embodiments, the cryoprobes preferably comprise a distal operating head which includes a thermally conductive outer sheath having a closed distal end and a chamber formed within the sheath, the operating head being adapted to be inserted into a body and to effect cryoablation thereat. The chamber serves as a reservoir for housing a fluid in contact with at least a portion of the outer sheath of the distal operating head.
According to still further features in the described preferred embodiments, the cryoprobes are designed and constructed coupleable to at least one high-pressure gas source, and preferably to a first gas source and also to a second gas source. The first gas source provides a first gas, which is cooled by expansion and may liquefy when passed through the Joule-Thomson orifice. A second gas from said second gas source has an inversion temperature lower than a temperature obtained by liquefaction of said first gas.
According to still further features in the described preferred embodiments, the cryoprobes are designed and constructed so that gas from the high-pressure gas source, while in a first temperature state prior to passing through a Joule-Thomson orifice, exchanges heat with gas from the high-pressure gas source which is in a second temperature state subsequent to having passed through the Joule-Thomson orifice. Control elements are provided for regulating the flow of gas from the first gas source and from the second gas source.
According to still further features in the described preferred embodiments, at least one of the plurality of cryoprobes is designed and constructed so as to expand laterally away from the introducer when deployed. Preferably, at least some of the plurality of cryoprobes are designed and constructed to advance, during deployment, in a plurality of different directions. Also preferably, each cryoprobe deploys from the introducer according to a predetermined path, and the plurality of cryoprobes are designed and constructed to be deployed laterally away from the introducer to form a predetermined arrangement of deployed cryoprobes. The plurality of cryoprobes, designed and constructed to advance from within the introducer and deploy in a lateral direction away from a periphery of the introducer, thereby define a three-dimensional cryoablation volume, which may be of predetermined shape.
According to still further features in the described preferred embodiments, each cryoprobe is retractable and advanceable in and out of the introducer. An advancing and retracting member may be operably coupled to one or more cryoprobe of the plurality of cryoprobes.
According to still further features in the described preferred embodiments, at least one cryoprobe of the plurality of cryoprobes has a sharp distal end.
According to still further features in the described preferred embodiments, at least one cryoprobe of the plurality of cryoprobes has a blunt distal end.
According to still further features in the described preferred embodiments, at least one of the plurality of cryoprobes comprises a Joule-Thomson heat exchanger. Preferably, the Joule-Thomson heat exchanger is coupled to a tube through which gasses enter the cryoprobe, the tube has an orifice located at a distal end of the tube, the orifice opens into a sheath which includes a thermally conductive material designed and constructed to conduct heat when the cryoprobe is in contact with a body tissue to be cryoablated. Preferably, the Joule-Thomson heat exchanger comprises a coiled tube housed within the thermally conductive sheath, and the Joule-Thomson heat exchanger further comprises a gas supply line on its proximal end and a gas outlet on its distal end, the outlet being in fluid communication with a chamber.
According to still further features in the described preferred embodiments, at least one of the plurality of cryoprobes comprises a heat-exchanging configuration. The heat exchaning configuration may include a porous matrix, which may include a conduit tunneling through at least a portion of the porous matrix, and which may include a spiral conduit integrated with the porous matrix.
According to still further features in the described preferred embodiments, at least one of the plurality of cryoprobes comprises a thermal sensor for monitoring local temperature conditions in areas in close proximity to the sensor. Preferably, at least one of the plurality of cryoprobes further comprises a feedback control system coupled to a gas source and to the thermal sensor, the feedback system is responsive to a detected characteristic from the thermal sensor and serves for controlling a rate of delivery of gas from the gas source to the cryoprobe. The thermal sensor is preferably positioned at the distal end of the cryoprobe, and may include a thermocouple.
According to still further features in the described preferred embodiments, at least one of said plurality of cryoprobes comprises a shape memory alloy material. The shape memory alloy material displays stress induced martensite behavior at a deployed position. The shape memory alloy material is in a non-stress induced martensite state when said cryoprobe is positioned in the introducer prior to deployment of the cryoprobe outside the introducer. Preferably the shape memory alloy material is an alloy of nickel titanium.
According to still further features in the described preferred embodiments, a cross section of each of said plurality of cryoprobes is between 0.3 mm and 3 mm.
According to another aspect of the present invention there is provided a method of cryosurgery comprising: (a) introducing into a body of a patient an introducer having a hollow and a distal portion being sufficiently sharp so as to penetrate into the body of the patient, the hollow of the introducer containing a plurality of cryoprobes each being capable of effecting cryoablation, each of the plurality of cryoprobes is deployable through the distal portion of the introducer; (b) deploying at least one of the plurality of cryoprobes; and (c) cryoablating a tissue of the patient with at least one of the plurality of cryoprobes.
According to further features in preferred embodiments of the invention described below, the step of cryoablating a tissue of the patient with at least one of the plurality of cryoprobes is accomplished by supplying a high-pressure gas to at least one of the plurality of cryoprobes, and cooling the cryoprobe by passing the gas through a Joule-Thomson orifice in a Joule-Thomson heat exchanger within the cryoprobe.
According to still further features in the described preferred embodiments, the cryosurgery method further comprises the step of cooling the gas within the body of the introducer prior to passing the gas through a Joule-Thomson orifice in the Joule-Thomson heat exchanger within the cryoprobe.
According to still further features in the described preferred embodiments the cryosurgery method further comprises heating at least one of the plurality of cryoprobes prior to removing the cryoprobe from a site of cryoablating of a tissue of the patient.
According to still further features in the described preferred embodiments the cryosurgery method further comprises the step of deploying at least several cryoprobes, thereby defining a three dimensional cryoablation volume, and cryoablating the volume so defined. Preferably, an imaging device is used to position at least one of the plurality of cryoprobes with respect to a tissue to be cryoablated. Preferably, the imaging device is selected from the group consisting of an ultrasound device, a computerized tomography (CT) device, a closed magnetic resonance imaging (MRI) device, an open magnetic resonance imaging (MRI) device, a fluoroscope device and an X-ray device.
According to still further features in the described preferred embodiments the cryosurgery method further comprises the step of inducing fast cyclical temperature changes in a deployed cryoprobe, such that a temperature of said probe alternates rapidly between a temperature of approximately 0xc2x0 C. and a temperature below xe2x88x9240xc2x0 C.
The present invention successfully addresses the shortcomings of the presently known configurations by providing a method and apparatus for cryoablation that provides for the destruction of a defined volume of tissue, yet minimizes damage to adjacent tissues.
The present invention further successfully addresses the shortcomings of the presently known configurations by providing a method of cryoablation using an apparatus that creates an extended volume of cryoablation yet is contained within a single introducer.
The present invention still further successfully addresses the shortcomings of the presently known configurations by providing an apparatus having an introducer which could be introduced through an operating channel of a catheter or cystoscope, enabling it to reach the proximity of the region to be treated with a minimum of trauma to intervening tissues.
The present invention yet further successfully addresses the shortcomings of the presently known configurations by providing a cryoablation apparatus and method which enables the pre-cooling of a plurality of cryoprobes within a single introducer, such that the pre-cooling stage of a two-stage Joule-Thomson heat exchange process can take place in close proximity to a second stage of cooling which takes place within the individual cryoprobes.
Implementation of the method and the apparatus of the present invention involves performing or completing selected tasks or steps manually, automatically, or a combination thereof. Moreover, according to actual instrumentation and equipment of preferred embodiments of the method and apparatus of the present invention, several selected steps could be implemented by hardware or by software on any operating system of any firmware or a combination thereof. For example, as hardware, control of selected steps of the invention could be implemented as a chip or a circuit. As software, control of selected steps of the invention could be implemented as a plurality of software instructions being executed by a computer using any suitable operating system. In any case, selected steps of the method of the invention could be described as being controlled by a data processor, such as a computing platform for executing a plurality of instructions.